Wind power is considered one of the cleanest, most environmentally friendly energy sources presently available, and wind turbines have gained increased attention in this regard. A modern wind turbine typically includes a tower, a generator, a gearbox, a nacelle, and one or more rotor blades. The rotor blades capture kinetic energy from wind using known foil principles and transmit the kinetic energy through rotational energy to turn a shaft coupling the rotor blades to a gearbox, or if a gearbox is not used, directly to the generator. The generator then converts the mechanical energy to electrical energy that may be deployed to a utility grid.
Wind turbine rotor blades generally include a body shell formed by two shell halves of a composite laminate material. The shell halves are generally manufactured using molding processes and then coupled together along the corresponding edges of the rotor blade. In general, the body shell is relatively lightweight and has structural properties (e.g., stiffness, buckling resistance and strength) which are not configured to withstand the bending moments and other loads exerted on the rotor blade during operation. In addition, wind turbine blades are becoming increasingly longer in order to produce more power. As a result, the blades must be stiffer and thus heavier so as to mitigate loads on the rotor.
To increase the stiffness, buckling resistance and strength of the rotor blade, the body shell is typically reinforced using one or more structural components (e.g. opposing spar caps with a shear web configured therebetween) that engage the inner surfaces of the shell halves. The spar caps are typically constructed fiber laminate composites that are tapered and blended to a very thin section as the spar caps approach the blade root of the rotor blade. For example, as shown in FIG. 4, a partial, cross-sectional view of a traditional spar cap 2 near a blade root 3 of a rotor blade 1 is illustrated. As shown, the spar cap 2 is tapered and blended to a very thin section as the spar cap 2 approaches the blade root 3 of the rotor blade 1. In addition, the blade root 3 is thickened to form the blade root buildup section 4 that absorbs the loads fed into the root 3 by the spar cap 2. More specifically, as shown, the blade root 3 is thickened such that holes can be drilled into the root 3 for corresponding barrel nuts 5 and blade bolts 6. In additional blade designs, the blade root 3 is thickened such that metal inserts can be integrated into the blade root 3 and corresponding blade bolts 6 can be inserted therethrough. In either case, the tension loads are transferred from the spar cap 2 to the blade bolts 6 on to the root face of the rotor blade for compression loads.
Understandably, thickening the blade root adds additional weight and costs to wind turbines rotor blades. Thus, the art is continuously seeking new and improved spar caps that reduce the weight and costs associated therewith.